1. Field of Invention
The present invention relates to a production apparatus of a semiconductor device, more specifically to a production apparatus which is appropriate for the rapid thermal processing (RTP) of large-diameter wafers, particularly 8 to 12 inch wafers. The present invention also relates to a production method of a semiconductor device by RTP.
2. Description of Related Art
At present, a variety of RTP apparatuses, the heating source of which are lamp, is commercially available. However, the heat mass of such lamp is small, and, although a wafer can be heated and cooled at a high rate by this method, the temperature uniformity is inferior to that attained by the other heating means. The lamp heating source, therefore, involves a problem in that it is liable to formation of slip lines, particularly on a large-diameter wafer.
U.S. Pat. No. 4,857,689 issued to Lee notes that RTP by means of a lamp has a drawback in temperature distribution on the wafer surface and hence cannot attain uniform and reproducible processing results. An RTP apparatus proposed in U.S. Pat. No. 4,857,689 comprises a longitudinal processing tube made of quartz and having a closed top, a heater provided on the upper portion of the processing tube, a wafer-supporting means capable of vertically displacing the wafer in the processing tube, and a micro-computer for controlling the wafer-displacing speed and wafer-temperature depending upon the wafer position.
Japanese Unexamined Patent Publication No. 60-67,672 proposes a heating apparatus which comprises a high-temperature heating region, a low-temperature heating region, and a cooling body interposed between these two regions. A steep temperature gradient between the two regions can be provided by the cooling body. The high- and low-temperature heating regions are assumed to be set at 850.degree. and 750.degree. C., respectively, and the temperature gradient attained is 5.degree. C./mm.
It is not easy by means of the heating apparatuses of the prior art to uniformly heat a large-diameter wafer to a desired temperature, to rapidly elevate or lower the temperature, and to keep the height of the apparatus as short as possible. For example, in the above mentioned U.S. Pat. No., since the temperature of the lower portion of the furnace, where a heater is not arranged, is set at an extremely low level, it is difficult for chemical vapor deposition (CVD) to be carried out in the lower portion.
Along with an enhanced integration, future semiconductor devices call for annealing at temperature as high as 1100.degree. C. and in as short a time as possible. Since heat transmission by radiation prevails at a temperature above 900.degree. C., an intermediate cooling body as is proposed in Japanese Unexamined Patent Publication No. 60-67,672 cannot attain a steep temperature gradient. For example, in the case where the temperature difference is 350.degree. C. (high temperature--1050.degree. C., low temperature--700.degree. C.), the intermediate region between the high- and low-temperature regions becomes as long as 350 mm or more, so that the overall length of the heating apparatus becomes very long.